U.S. Pat. No. 3,819,388, having the same inventor as the present invention, describes a process for forming lightweight cellular cementitious compositions from a mineral cement, a lightweight mineral aggregate, a nonionic surfactant, water, and, optionally, polyvinylacetate. The nonionic surfactant acts as a bubble forming additive to provide a cementitious composition that has a cellular structure with equal distribution of cells throughout the composition. The nonionic surfactant can be combined with an anionic surfactant in use. The water is utilized in the processing and is required to render the cement settable.
U.S. Pat. No. 4,077,809 describes improvements in the stabilization of aqueous foamed compositions which involve the incorporation of certain synthetic resin emulsions which are film formers at room temperature into an aqueous foaming composition. The synthetic resin and plasticizer components of these emulsions have a glass transition temperature of about 10.degree. C.-25.degree. C. Suitable components in these emulsions are vinyl acetate, an acrylate homo-, co- or terpolymer, and styrene butadiene resins.
The present invention involves further improvements to foamed cementitious products as described above and the procedure utilized to produce such products. The particular features and advantages of the present invention will become apparent from the description below. The foamed cementitious compositions of the present invention can be formed into final products utilizing conventional techniques such as pumping, spraying, casting or trowelling to provide settable lightweight cellular compositions. The compositions of the invention, however, provide final products having densities which are appreciably less than the density of a conventional mix of mineral cement and aggregate. For example, the portland and calcium aluminate cement compositions of the present invention can be produced in a range of 20-90 pounds per cubic foot air-dry densities, while the gypsum cement compositions of the invention can be produced in a range of about 12-30 pounds per cubic foot.